Ultra-reliable and low-latency communications (URLLC) is envisioned to support mission critical applications with stringent requirements of latency and reliability, where the codeword is required to be short, e.g., the order of 100 channel uses. Specifically, with the aided of the full-duplex receiver, the authors in [1]} showed that transmitting AN with a fixed power is still helpful in covert communication with finite blocklength, since in a limited time period the warden cannot exactly learn its received power. The blocklength has significant impact on the detection performance at Willie and the maximal achievable rate of the channel from Alice to Bob (i.e., the maximal achievable rate decreases as blocklength decreases for a fixed decoding error probability).
